About half of all cancer deaths in the United States result from aerodigestive cancer. For example, of the estimated 564,800 annual cancer deaths, 160,100 (25%) result from lung cancer; 56,500 (10%) result from colorectal cancer; 28,900 (6%) result from pancreas cancer; 13,700 (3%) result from stomach cancer; and 11,900 (3%) result from esophagus cancer. In addition, over 7 percent of the annual cancer deaths result from other aerodigestive cancers such as naso-oro-pharyngeal, bile duct, gall bladder, and small bowel cancers (Landis et al., CA Cancer J. Clin., 48:6-29 (1998)).
Attempts have been made to identify and use nucleic acid markers that are indicative of cancer. For example, mutations in the p53 cell cycle regulator gene have been associated with numerous cancers, especially colorectal cancer, and it has been suggested that specific mutations might be a basis for molecular screening assays for the early stages of certain types of cancer. See, e.g., Sidransky, et al., Science, 256: 102-105 (1992).